The Archimedean Screw

To the Editor

A sign at the exhibition Babylon at the British Museum in London (November 2008–March 2009) informed visitors that the Archimedean screw was probably invented in Iraq. The obvious source for this belief is an article by Stephanie Dalley. It is therefore necessary to examine her arguments, which derive, in the first instance, from her interpretation of an inscription in Akkadian. Dalley asserted that the inscription shows that Sennacherib (reigned 704–681 bce) used bronze water screws to irrigate the gardens of Nineveh. She suggested that the water screws could have been supported in a manner similar to the way in which near-contemporary, huge bronze-banded doors were held in position and that any leaking water would lubricate the supports for the screws.¹ In support of this assertion, she invoked Sennacherib’s well established mastery of water engineering and of bronze casting.² Dalley did acknowledge that the bronze screws might have been preceded by wooden ones, but she thought that wood was too scarce to be employed generally. She further claimed that the Assyrians were familiar with the spiral, by illustration of one on a brick column.³ To complete her case, she claimed that the “Hanging Gardens of Babylon” were actually at Nineveh.⁴

Creating gardens was an established practice of the rulers of Nineveh and other cities in ancient Mesopotamia. Nothing has been found in any excavation that confirms that they existed, though more than one suggestion has been put forward.⁵ There is no sign of them on the very early maps of Babylon. ⁶ Herodotus (b. 480–490 bce) did not mention them. He did refer to a spiral way to the top of what is now taken to be a ziggurat, and he described the use of the shaduf (hand-operated lever) for irrigation on the river.⁷

Nonetheless, despite this shift in place, Dalley quoted two authors as directly supporting her assertion, though both of them referred to Babylon: Strabo (ca. first century ce), Geography 16.1.5, and Philo of Byzantium, On the Seven Wonders of the World. She also claimed that Diodorus Siculus (fl. 60–30 bce) (History 2.10.6) gave a similar description of the gardens, again at Babylon.⁸ She suggested that chains wrapped around the cylinders created enough friction to operate them. Men or machines turned the screws’ cylinders.⁹ In addition, water leaking from the cylinders could have helped to lubricate the screws. Her text calmly recorded: “Nevertheless, the recognition that a helical form hidden inside a cylinder could be used to raise water is a significant conceptual leap.”¹⁰ She concluded that these arguments for bronze water screws made technological sense.¹¹

They do not. There is more than a “significant conceptual leap” in that quotation about the helical form. If it were correct, it would be an astounding one! The spiral she illustrated is a very simple one, with the curve convex, whereas the cochlea is one of the most complex of the large family of spirals and spiraloids—technically it is a three-dimensional spiral and its curve is internal. To assume the latter was discovered before 600 bce, long preceding the much simpler endless screw, requires an extraordinary leap of the imagination. In addition, those bronze screws weighed between two and three tons.¹² Bronze chains would have added still more weight. They could not have provided a feasible method of turning the screws; in fact, Dalley omitted to report that the bronze water screw cast for the BBC2 program“ The Hanging Gardens of Babylon,” for which she was a technical adviser, could not be turned.

Leaking water is not likely to have been a lubricant; depending on its hardness, any deposit from the water would have increased rather than diminished the friction. Oil and water together would form a rather nasty mix. An apparent lack of information on the actual dimensions of the gardens, particularly the height, was brushed aside with a comment about the absence of statistics. Yet there is agreement between two of her quoted sources that their height...